[mpich-discuss] MPI_PUT Implementation Bug or Pilot Error?

[Rajeev Thakur]

MPI_Put is nonblocking. You are changing the contents of the source buffer before the put is complete.

Rajeev

On Mar 29, 2013, at 12:01 PM, Timothy Stitt wrote:

> Hi all,
> 
> I've come across some strange behavior with a code that uses MPI_PUT(). I can confirm that this problem appears in older MPICH2 v1.4.x releases as well as the latest MPICH v3.0.3 release. I can also confirm that I receive the correct results when using Open MPI.
> 
> I am attaching a reproducer code below that simulates the problem I am having (following the code will hopefully explain its purpose better than what I can describe here in a few lines). This case is hardcoded for a 4-process run. For some reason MPICH implementations are losing some data elements and duplicating others after the communication is complete. I would be grateful if someone can confirm whether this is indeed an implementation bug or a subtle problem with how I've implemented the one-sided communication.
> 
> Thanks in advance,
> 
> Tim.
> 
> program reproducer
> 
>  use mpi
> 
>  implicit none
> 
>  integer :: error,dum_com(2),my_rank,i
>  integer :: win_values_points, type_integer,NProc=4
>  INTEGER(KIND=MPI_ADDRESS_KIND) :: win_values_size, target_disp
>  integer,allocatable :: neighbor_values(:), ncount_in(:)
> 
>  call MPI_INIT(error)
>  call MPI_COMM_RANK(MPI_COMM_WORLD,my_rank,error)
> 
>  CALL MPI_Type_size(MPI_INTEGER,type_integer,error)
> 
>  ! Calculate Size Of Window (in bytes)
>  win_values_size=2*type_integer*NProc
> 
>  ! Allocate Window Storage
>  allocate(neighbor_values(0:2*Nproc-1))
>  neighbor_values=0
> 
>  ! Define Input Values
>  allocate(ncount_in(NProc))
>  if (my_rank .eq. 0) ncount_in = (/1,2,3,4/)
>  if (my_rank .eq. 1) ncount_in = (/5,6,7,8/)
>  if (my_rank .eq. 2) ncount_in = (/9,10,11,12/)
>  if (my_rank .eq. 3) ncount_in = (/13,14,15,16/)
> 
>  ! Create Window
>  CALL MPI_WIN_CREATE(neighbor_values, win_values_size, type_integer, MPI_INFO_NULL, MPI_COMM_WORLD, win_values_points, error)   ! Create Neighbor Storage Win
> dow
>  call MPI_Win_Fence(0,win_values_points,error)
> 
>  ! Print pre-communication data
>  print*,my_rank,ncount_in
>  call flush(5)
>  call MPI_BARRIER(MPI_COMM_WORLD,error)
> 
>  ! Communicate Data Values to all proceses
>  do i = 1,4
>     target_disp=2*my_rank
>     dum_com(1)=ncount_in(i)
>     dum_com(2)=99
>     CALL MPI_PUT(dum_com,2,MPI_INTEGER,Nproc-i,target_disp,2,MPI_INTEGER,win_values_points,error)
>  end do
> 
>  call MPI_Win_Fence(0,win_values_points,error)
> 
>  ! Print post-communication values
>  print *
>  print *,my_rank,neighbor_values
>  call flush(5)
>  call MPI_BARRIER(MPI_COMM_WORLD,error)
> 
>  ! Free Window Storage
>  call mpi_win_free(win_values_points,error)
> 
>  call MPI_FINALIZE(error)
> 
> end program reproducer
> 
> 
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